Noiseless escapement mechanism



Oct. 11, 1949. c VELTMAN ETAL 2,484,198

NOISELESS ESCAPEMENT MECHANISM Filed Dec. 13, 1945 3 Sheets-Sheet l Oct. 11, 1949. J. c. VELTMAN ETAL NOISELESS ESCAPEMENT MECHANISM Filed Dec. 15, 1945 5 Sheets-Sheet 2 Oct. 11, 1949. J. c. VELTMAN ET AL NOISELESS ESCAPEMENT MECHANISM 5 Shets-Sheet 5 Filed Dec. 15, 1945 Patented Oct. 11, 1949 liNlTED STATE-S? ere-NT OFFICE Louis Cun'ty, lVIo., assig'irors to The Emerson Electric Mfg. 00., St. Louis, Mo., a corporation of Missouri Application December 13, 1945 Serial No. 634,757

(01. revea)" Claims.

This invention relates to improvements in typewriters and, more particularly, to the escapement mechanism for such machines.

An object of the invention is to provide, in association with the escapement mechanism of type writing machines, an efficient and compact device whereby the return movement of the paper carriage may be effected without producing the usual noise'or click that results from the escapement pawl contacting with the teeth of the escapement wheel during the reverse or return movement of the paper carriage of the machine.

Another object of the invention is to provide a device of the kind mentioned which is automatically operated incident to the return movement of the paper carriage, which device is associated in such a manner with the standard parts of the escapement mechanism of a typewriter as to avoid any substantial increase in frictional load on the normal operation of the typewriter mechanism.

Another object of the invention is to provide, in association with the device tending to reduce the usual noise incident to the paper carriage return, a device to render such device inoperative When the reverse movement of the paper carriage is under the control of the backspace device.

Another object of the invention is to provide a device of this type which is embodied in the escapement mechanism of the typewriter in such a manner as that it is readily accessible for repair, replacement or adj ustnient without disassembling other parts of the mechanism.

Other objects and advantages of the invention will appear from the following detailed description thereof taken in connection with the accompanying drawings, in which:

Fig. 1 is a skeletonized isometric view of those parts of a typewriter designed to illustrate the environment for the mechanism of the invention;

Fig. 2 is a top plan view of the lower rail assembly including the spring motor and the escapement mechanism;

Fig. 3 is a bottom plan view of the assembly illustrated in Fig. 2;

Fig. 4 is a top plan view of the escapement mechanism shown in the position assumed during the return movement of the paper carriage during which the escapement pawl is disengaged from the escapem'ent wheel;

Figx5 is a side elevation of the'spring motor barrel and associated parts with portions or the lower rail assembly being broken;

Fig.6 is an isometric View of 'th'e'lower rail and escapement assembly with the springmotor assembly exploded to show'the relationship and the structure of the parts thereof;

Fig. 7 is an isometric view of the e'scapement assembly and related parts of the backspace device;

Fig. 8 is an enlarged cross-sectional view on the line 3-8 of Fig. 1 to more fully illustrate the escapement and its association with related parts of the mechanism;

Fig. 9 is an isometric view, partly in section, of the back plate of the spring motor housing; and

Fig. l0'is an elevation illustrating the detail construction of a support for a link bar con meeting a friction disc with the escapement pawl.

The selected environment of the invention is in" a typewriting machine of the general c'zonstru'c tion disclosed in our copending application, Serial No. 612,772, filed August 27, 1945.

Generally stated, the type of machine illustrated is one in which the movement of the paper carriage is controlled by a spring motor and an es'capem'e'nt which includes an escape'men't wheel and an escapement pawl operatively connected for operation as an incident to the normal se-' queries of 'part movements resulting from the usual functioning of the machine. This. form of escapement is employed for the purposes of illustration only as the invention is applicable to other es' c'ape'ment mechanisms, employing a motor which has reverse movement as an operative element of the machine in the control of the movement of the paper carriage.

In order that the manner in which the device of the present invention is incorporated with a typewriting machine of this type may be readily understood, certain of the standard parts will be referred to in order to clarify the relationship o the novel combinations thereto.

Ina typewriting machine of the type selected for illustration, there is included a lower rail member suitably supported in the frame of the machine and constituting a part of the general paper carriage assembly, which lower rail member includes side members I connected by a central plate or web 2, forming the bottom wall of the lower rail structure. The bottom wall 2 is provided with cutout sections 3, 4 and 5.

An escapement plate comprising a central section 6, having a bifurcated extension I at one end and a similar bifurcated section 8 at the opposite end, is secured to the underface of the wall 2 of the lower rail member below the opening 4 by screws 9 and I passing through openings in the arms of the bifurcated extensions 1 and 8 of said plate, respectively.

A stud l I (Fig- 8) is riveted to the central section 6 of the escapement plate, which stud ex-. tends upwardly therefrom and through the opening 4. The stud H has journaled thereon an escapement wheel l2 and a pinion 13 mounted upon the periphery of the hub of said escapement wheel so that the two members are unitary for cooperative rotation on the stud, which constitutes the common axis thereof. v

In this same assembly, and positioned below the underface of the escapement wheel and the uppper wall of the central section of the escapement plate, is a bell crank I4 which constitutes a part of the backspace mechanism, later to be described. These parts just mentioned are retained in. removable relationship by aretaining screw I5.

The upper rail member, which includes side members [6 and an upper wall I I having cutouts I8, I9, and 2| therein, is mounted for shiftable movement in interfitting relation with the lower. rail member and constitutes the paper carriage that supports a platen 22.. This paper carriage assembly will be recognized to be of standard construction in which the rear one of the rails or side members l6 carries a rack 23, which meshes with the pinion l3, as will be understood, during the normal operation of the typewriting machine.

The step by step feed motion of the paper carriage, through the rack and pinion connection, actuates the escapement wheel l2 in a counterclockwise direction. The free rotation, however,

of the escapement wheel is intermittently, r estrained by an escapement pawl 24,.which includes a detent arm and an arm 26, which together constitute a bell crank lever pivoted to the top face of the escapement plate in a cooperative position in respect of the escapement wheel. The depth of the engagement of the detent arm 25, successively with the teeth of the escapement wheel, is madeadjustable, and is determined by the setting of an eccentric stop 2! in the form of a. headed rivet having a tooled slot therein mountedin one of the arms 8 of the escapement plate.

In thevoperation of the escapement pawl, a spring 28, connecting the escapement pawl with the secondary escapement pawl 29 of the escapement mechanism, normally tends to rotate the escapement pawl in a clockwise direction and against the stop device 21, which position of the parts is illustrated in Fig. 7, that is to say, in the step by step forward movementof the paper carriage in the normal operation of the typewriter, either under the control of the universal bar or the space bar, the detent arm 25 will tend to engage successively with the teeth of the escapement wheel. This relationship, unless modified and controlled both on the forward and retion a recognized, objectionable noise or click.

It is with the elimination of this objectionable feature of the standard operation of typewriting machines of this class with which the struc-- ture of the present invention primarily deals.

The paper carriage, as is usual in machines of this type, is actuated by a spring motor of known internal construction, which motor includes a housing or barrel indicated by 30 in the form of a reel, and which is mounted on and secured to a bracket 3i supported by the underface of the plate 2 adjacent to the cutout portion 5 in said plate.

The spring motor housing 30 carries a cylindrical hub 32 (Fig. 9) projecting inwardly from its inner wall. A friction disc 33 is mounted on the hub 32, said friction disc being provided with an ear 34 formed with an offset shoulder, which ear extends outwardly from the periphery of said disc. The disc is also provided with an angular arm 35, likewise extending outwardly from the body of the disc and positioned approximately at right angles to the ear 34, which arm 35 extends rearwardly from the periphery of the disc. Thedisc 33 is lightly held against the rear wall of the housing 33 by a spring washer 36. These parts are assembled and are held on the hub 32 by an internally threaded ring 31, which mounts over the rear threaded end of the hub 32.

A link 38 is pivoted at one end to the ear 34,

and extends inwardly from its pivot point to a point adjacent to an angular arm 39, which extends forwardly from the escapement pawl 24 in such a position that when the link 38 is moved inwardly, incident to the return movement of the, paper carriage, the upstanding angular leg of the arm 39 contacts a rearwardly bent ear 40 on the inner. extremity of the link 38. The link 38 is supported for sliding movement in response to the movement of the friction disc by supporting its free extremity adjacent to the ear 4!) in a bracket 4| extending upwardly from the upper face of the escapement plate 6. The rotation of the spring motor housing 30 is responsive to the movement of the carriage since a length of a flexible connection of suitable material, such as cord or thin wire 42, is wound upon the spool or reel section of the housing, and the free end of which is carried transversely of the carriage and attached thereto by engagement with an. ear 43 projected from the wall of the plate ll of the upper rail member, and into the cutout section I 8.

During the return movement of the carriage assembly, the sprin motor housing rotates in a clockwise direction, imparting .a rocking movement in the same direction to the friction disc 33. This moves the link 38 to the right of the machine and causes the ear 40 to contact with the upstanding leg of the arm 39 of the escapement pawl 24, thereby rocking the escapement pawl counterclockwise and restraining it from opposite movement, resulting in moving and holding the arm 25 of the escapement pawl out of the path of movement of the escapement wheel i2 during the return movement of the carriage. This prevents the arm 25 from contacting the successive teeth of the escapement wheel as it is rotated clockwise incident to the return movement of the carriage, eliminating the noise due to the click of the pawl on the escapement wheel teeth.

As this operation is brought about by the light frictional engagement of the friction disc with the wall of the housing of the spring motor, it

functions without substantially increasing any frictional load on the parts during the return movement of the carriage.

It willbe noted that in order to facilitate the accurate movement of the link 38, a small plate is mounted on the top face of the bottom wall of the lower rail assembly, which plate has a pair of spaced, upwardly and forwardly directed ears 45, spaced apart and in the path of movement of the arm 34. These ears constitute stops limiting the rocking movement of the arm 34 and, thereby, the extent of movement of the link 38. Thus, the extent of rocking movement imparted to the escapementpawl is adjusted to permit it to move withinand without the path of movement of the teethon the escapement wheel.

While it is not a part of the invention, for the sake of completeness, there is illustrated in the drawings a standard form of means for tensioning the springs of the spring motor. This structure includes a detent 45, a ratchet 41, and screws (l8 and A9, said last-mentioned parts being assembled in operative relationship with the spring motor and being mounted upon the rear face of the bracket that supports the springimotor housing, providing means for retaining the parts in operative relationship.

It will be understood that, after the paper carriage has been returned to its normal starting position, the spring motor provides theforce' tending to move the paper carriage in the normal step by step feed movement. This movement reverses the movement of the friction disc 33 and thereby moves the link 38 to the left, carrying the ear ill, at its extremity, out of detent relationship with the arm 39, thereby permittin the escapement pawl to reengage successively with the teeth of the escapement wheel in the step by step feed of the carriage.

Since the foregoing construction interferes with the normal operation of the standard backspacing mechanism because, during the operation, the escapement wheel overruns slightly the L 33' from moving with the barrel 3c of the spring motor when it rotates incidental to a backspacing operation.

In order to permit proper functioning of the backspace mechanism, the arm 35 on the disc 33 engages the undersurface of an arm 50, formed on a lever 51 pivoted at 52 to the underface of the bottom wall of the lower rail assembly. The free end of the lever 5i is connected by a link 53 with the backspace bell crank M, to which reference has heretofore been made. Therefore, during a backspacing operation, the lever 53 is moved to the left, operating the bell crank it of the backspace mechanism clockwise, which movement causes a cam face extremity 54 of the arm 50 to ride over the top edge of the arm 35 on the friction disc 33, restraining it from movement and thereby maintaining the friction disc 33 in its normal position, preventing movement of the link 33 and, thereby, during the back space operation, leaving the escapement pawl to operate in its normal manner.

From the foregoing description, it will now be understood that the construction fully accomplishes the purposes hereintofore set out.

It will also be understood that the invention is not to be confined to the'exact form and construction of the parts shown and described, but that the principles of the invention for accom plishing the novel' purposes may be modified in certain particulars without departing from the invention.

It is, therefore, not to be understood that the invention is limited except to the extent of the combinations expressed in the claims.

What-we claim. and desire to secure by Letters Patent is:

1'. Ina typewriting machine, the combination with ashifta-ble paper carriage, an escapement mechanism having an escapement wheel and an escapement pawl normallymoved to contact said escapement wheel, and a spring motor having a revoluble reel housing operatively connected to the carriage to power the feed thereof, of an escapement click elimination mechanism comprising a friction disc in contact with thereel housing and adapted to be rotated thereby, an arm secured to said disc and extending outwardly therefrom, spaced ears mounted adjacentsa-id housing and disposed on opposite sides ofsaid arm'adapted to be contacted by said arm to limit movement thereof and therethrough rotary movement of said disc, a longitudinally movable link pivotally connected to said arm, said link extending to a point adjacent the escapement pawl, and anarm secured to said escapement pawl and extending into the path of movement of said-link adapted to be contacted by'said link whensaid link is moved by carriage return rotation of said reel housing to move the escapement pawl out of contact with the escapement wheel, whereby the usual escapement clicking noise is eliminated during carriage return.

2. In a typewriting machine, the combination with a shiftable paper carriage, an escapement mechanism having an escapement wheel and an escapement pawl normally moved to contact said escapement wheel, and a spring motor having a revoluble reel housing operatively connected to the carriage to power the feed thereof, of an escapement click elimination mechanism comprising a friction disc in contact with thereel housing and adapted to be rotated thereby, an arm secured to said disc and extending outwardly therefrom, means limiting rotation of said friction disc, a longitudinally movable link pivotally connected to said arm, said link extending to a point adjacent the escapement pawl, and an arm secured to said escapement pawl and extending into the path of movement of said link adapted to be contacted by said link when said link is moved by carriage return rotation of said reel housing to move the escapement pawl out of contact with the escapement wheel, whereby the usual escapement clicking noise is eliminated during carriage return.

3. In a type-writing machine, the combination with a shiftable paper carriage, an escapement mechanism having an escapement wheel and an escapement pawl normally moved to contact said escapement wheel, and a spring motor having a revoluble reel housing operatively connected to the carriage to power the feed thereof, of an escapement click elimination mechanism comprising a friction disc in contact with the reel housing and adapted to be rotated thereby, an arm secured to said disc and extending outwardly therefrom, means limiting rotation of said friction disc, and a longitudinally movable link pivotally connected to said arm, said link extending to a point adjacent the escapement pawl, the escapement pawl including a portion extending into the path of movement of said link adapted to be contacted by said link when said link is moved by carriage return rotation of said reel housing to move the escapement pawl out of contact with the escapement wheel, whereby the usual escapement clicking noise is eliminated during carriage return.

4. In a typewriting machine that includes a paper carriage mounted for reversible shiftable 1 movement, an escapement mechanism including an escapement wheel and an escapement pawl for controlling the forward step by step feed of the carriage, a back space device for reversing the normal movement of the escapement wheel to reverse the movement of said paper carriage, and a spring motor for actuating the carriage, the combination comprising a noise elimination device associated with the spring motor to disengage the escapement wheel and pawl during the normal reverse movement of the paper carriage, and a device controlled by the back space device to render said noise elimination device inoperative during reverse movement of the paper carriage when actuated by said back space device.

5. In a typewriting machine that includes a paper carriage mounted for reversible shiftable movement, an escapement mechanism including an escapement wheel and an escapement pawl for controlling the forward step by step feed of the carriage, a back space device for reversing the normal movement of the escapement wheel to reverse the movement of said paper carriage, and

a spring motor for actuating the carriage, the

combination comprising a noise elimination device associated with the spring motor to disengage the escapement wheel and pawl during the normal reverse movement of the paper carriage including a friction disc rotatable a limited degree in each direction by the spring motor and having an outwardly extending arm, and a device controlled by the back space device to render said noise elimination device inoperative during reverse movement of the paper carriage when actuated by said back space device including an arm secured to the back space device and movable into the path of the friction disc arm to 15 block movement of the same.

JOHN C. VELTMAN. WILLIAM C. MICHELSEN.

REFERENCES CITED- 20 The following references are of record in the file of this patent:

UNITED STATES PATENTS 

